JP6414231B2 - Microphone electronic circuit and method of operating a microphone - Google Patents

Description

  The present disclosure relates to an electronic circuit for a microphone. Specifically, the electronic circuit is configured as an ASIC (Application Specific Integrated Circuit). Furthermore, the present disclosure relates to a microphone including an electronic circuit. The microphone is created by MEMS technology (microelectromechanical system). Furthermore, a method for operating a microphone is disclosed.

  For various applications, the microphone operates in three-terminal mode. In the three-terminal mode, separate terminals are prepared for power, ground, and output. Another application requires a two-terminal mode. In the two-terminal mode, the power supply and output are assigned to the same terminal.

  An object of the present disclosure is to provide an electronic circuit and a microphone having improved characteristics. In particular, it is an object of at least some embodiments to allow operation of electronic circuits in various modes. Furthermore, it is an object of the present disclosure to provide an improved method of operating a microphone.

  One aspect of the present disclosure relates to an electronic circuit for a microphone. The electronic circuit is configured as an ASIC. The electronic circuit includes a first terminal. The first terminal is configured for power supply. Power is supplied to electronic circuit components such as transistors. Additionally or alternatively, power is provided to operate a transducer that can be connected to an electronic circuit.

  The electronic circuit includes a second terminal. The function of the second terminal depends on the selected mode of the electronic circuit.

  The electronic circuit includes a third terminal. The third terminal is configured for ground.

  In one embodiment, the electronic circuit operates in a first mode. In the first mode, the second terminal is not configured for microphone output. Instead, the second terminal is connected to ground. A capacitor may be provided to capacitively connect the second terminal to the ground. Capacitors also provide electromagnetic interference (EMI) protection. The microphone output is provided at the first terminal. Accordingly, in the first mode, the first terminal is configured for both power and microphone output. The third terminal is configured for ground. The first mode is also referred to as a two-terminal mode because the power supply, microphone output, and ground are assigned to two terminals.

  In one embodiment, the electronic circuit operates in the second mode. The second mode is a three-terminal mode. In the second mode, the second terminal is configured for microphone output. In response, the electrical output signal is supplied to the second terminal. In the three terminal mode, the first terminal is configured for power supply only. The second mode is also referred to as a three-terminal mode because the power supply, microphone output, and ground are assigned to three terminals.

  The electronic circuit is selectively operable in a first mode and a second mode. For this purpose, the electronic circuit is programmable to operate in the first or second mode.

  The electronic circuit includes a memory. The memory may be a non-volatile memory. The memory is configured to set the electronic circuit in the first or second mode. Specifically, the memory is programmable to select one of the modes. Further, the memory is configured to allow adjustment of microphone sensitivity.

  The electronic circuit comprises an adjustable load. Specifically, the electronic circuit comprises at least one switchable resistor. The switchable resistor is controlled by the memory. Specifically, the memory switches the resistor on or off. Here, “switchable” means that the amount of current flowing through the resistor can be specifically controlled by opening or closing the switch. “Switching off” or “deactivating” a resistor means allowing a small current to flow through the resistor. “Switching on” or “activating” a resistor means allowing a large current to flow through the resistor. The switchable resistor allows the sensitivity of each microphone electronic circuit to be adjusted to the target. By switching the resistor on and off, the same electronic circuit can be used in the first and second modes. In one embodiment, the switchable resistor is switched on in the first mode. The switchable resistor is switched off in the second mode.

  The operation of the electronic circuit in the first mode does not require an additional external resistor. Preferably, the electronic circuit is composed of an ASIC, and the switchable resistor is incorporated in the ASIC. This can reduce the space required for the electronic circuit. Built-in resistors can be made to increase little area. Furthermore, by incorporating a resistor into an electronic circuit, specifically, an ASIC, variations in microphone sensitivity can be reduced. Sensitivity variations are caused by tolerances of external components.

  The electronic circuit comprises at least one switch. A switch is used to activate or deactivate the switchable resistor. Specifically, the switch is controlled by a memory. Depending on the programmed mode, the memory opens or closes the switch. Thereby, the switchable resistor is activated or deactivated. In one embodiment, the switch is closed in the first mode. In the second mode, the switch is opened.

  In one embodiment, the switch is connected in series with a switchable resistor. The switch is closed to activate the resistor. The switch is opened to deactivate the resistor. The switch is closed in the first mode and opened in the second mode.

  As a further example, the switch is connected in parallel with a resistor. The switch is opened to activate the resistor. The switch is closed to deactivate the resistor. The switch is opened in the first mode and closed in the second mode.

  The electronic circuit comprises a signal input for receiving a signal from the transducer. In one embodiment, the switchable resistor is placed in the electrical path between the signal input and the second terminal. The switchable resistor is connected in parallel with the further resistor.

  In one embodiment, the switchable resistor is placed in the electrical path between the signal input and the third terminal. A switch is connected in parallel with the resistor.

  In one embodiment, the electronic circuit comprises two switchable resistors. The electronic circuit comprises two switches, each of which is assigned to one of the resistors. Specifically, for example, as described above, the electronic circuit includes a first switchable resistor connected to the third terminal and a second switchable resistor connected to the second terminal.

  In one embodiment, at least one switchable resistor is adjustable. Preferably, the memory controls the adjustment of the resistance. The adjustment makes it possible to adjust the sensitivity of the microphone. This allows the resistance to be set to a value that provides the sensitivity required by the customer in the two terminal mode. As a result, variations in sensitivity not only due to resistance but also due to variations in microphone sensitivity are reduced. Further, the current consumption and THD (total harmonic distortion) performance of the microphone can be adjusted by the adjustment. Specifically, the memory allows fine adjustment of the resistance.

  A further aspect of the present disclosure relates to a microphone with an electronic circuit and a transducer. The electronic circuit comprises any structural and functional features as described above. The features described for the microphone are also disclosed herein in connection with the electronic circuit, and vice versa, even if each feature is not specified in the context of a particular embodiment.

  The transducer is fabricated by application of MEMS technology. The transducer includes a capacitor. Specifically, an acoustic input signal causes a change in the capacitance of the transducer. That is, the microphone is a condenser microphone. The transducer comprises a diaphragm and one or more backplates. Specifically, the transducer is a single-ended or differential transducer.

  According to a further aspect of the present disclosure, a method for operating a microphone is provided. The method includes any functional and structural features of the microphone as described above. The features described for the microphone are also disclosed herein in connection with the method, and vice versa, even if each feature is not explicitly described in the context of a particular embodiment.

  The method includes selecting one of the modes. Specifically, selecting a mode means programming the memory to operate in the first or second mode. The method further includes operating the microphone in the selected mode.

  The method also includes adjusting at least one switchable resistor. As an example, fine adjustment of resistance is performed. To fine tune the resistance, the microphone is operated in the selected mode. At that time, for example, the parameters of the microphone are determined by measuring the microphone output. As an example, sensitivity, THD performance or current consumption is determined. Thereafter, the resistance value is adjusted by programming the memory. This makes it possible to optimize the microphone parameters.

  Further features, improvements and utilities will become apparent from the following description of exemplary embodiments in connection with the figures.

The circuit diagram of the electronic circuit 1 for the microphones 2 in the first mode is shown. The circuit diagram of the electronic circuit 1 for the microphones 2 in the second mode is shown.

  Similar elements, elements of the same kind and elements that perform the same function are denoted by the same reference numerals in the figures.

  1 and 2 show the microphone electronic circuit 1 in two different modes. In FIG. 1, the electronic circuit 1 is in the first mode, and in FIG. 2, the electronic circuit 1 is in the second mode.

  The electronic circuit 1 is an application specific electronic circuit (ASIC). The electronic circuit 1 is made as a die.

  The microphone 2 includes a transducer 3, specifically a MEMS transducer, in order to convert an acoustic input signal into an electrical signal. As an example, the transducer 3 may include a semiconductor material such as silicon or gallium arsenide. The transducer 3 includes a diaphragm and one or more back plates. As an example, the distance between the diaphragm and the back plate is in the range of 1 μm to 10 μm. The transducer 3 is configured as, for example, a differential transducer or a single-ended transducer.

  The microphone 2 includes a MEMS die and an ASIC die including the electronic circuit 1. The electronic circuit 1 shown is also used with other transducers other than MEMS transducers. The microphone 2 can be used for a headset, for example.

  The transducer 3 is electrically connected to the electronic circuit 1. Specifically, the electronic circuit 1 processes the signal of the transducer 3. As an example, the signal is processed by a transistor 20 that functions as an amplifier and / or a further component 21. Furthermore, the electronic circuit supplies a bias voltage to the transducer 3, which is not shown in detail in the figure.

  The electronic circuit 1 includes a first terminal 4 for connecting the electronic circuit 1 to a voltage source 5. A resistor 6 is disposed at a connection portion between the first terminal 4 and the voltage source 5. The resistor 6 is connected in series with the voltage source 5.

  The electronic circuit 1 includes a third terminal 7 for connecting the electronic circuit 1 to the ground. The transducer 3 is also connected to ground.

  The electronic circuit 1 includes a second terminal 8 having a function corresponding to the operation mode of the electronic circuit 1. Terminals 4, 7, and 8 are configured as pins.

  As shown in FIG. 1, the electronic circuit 1 can operate in a first mode which is a two-terminal mode. In the first mode, the second terminal 8 is not used as a microphone output. Instead, in the first mode, the second terminal 8 is connected to ground via a capacitor 9. The capacitor 9 is connected in series to the second terminal 8. The capacitor 9 is not a part of the electronic circuit 1 and specifically is not a part of the ASIC.

  As shown in FIG. 2, the electronic circuit 1 can also operate in the second mode, which is a three-terminal mode. In the second mode, the second terminal 8 is used as a microphone output. A capacitor is not connected to the second terminal 8. An electrical signal generated by the transducer 3 in response to the acoustic input is supplied to the second terminal 8.

  As can be seen in FIGS. 1 and 2, the electronic circuit 1 includes a memory 10 for enabling operation in the first or second mode. The memory 10 is a nonvolatile memory. The memory 10 includes a control input 11 and a clock input 12. The memory is programmable from the outside, specifically by accessing the control input 11 via a control pin. In response to an input signal supplied to the control input 11, the memory 10 switches the electronic circuit 1 to operate in the first or second mode.

  The electronic circuit 1 includes a first switchable resistor 13 and a second switchable resistor 14. The first switchable resistor 13 is connected to the third terminal 7. Specifically, the first switchable resistor 13 is connected in series to the third terminal 7. A further resistor 15 is connected in parallel with the first switchable resistor 13. The first switchable resistor 13 can be activated or deactivated by the first switch 16. In the second mode, the first switch 16 is open so that the first switchable resistor 13 is inactive.

  The second switchable resistor 14 is connected to the second terminal 8. The second switchable resistor 14 can be activated or deactivated by the second switch 17. The second switch 17 is connected in parallel with the second switchable resistor 14. In the second mode, the second switch 17 is closed so that the second switchable resistor 14 is bridged and deactivated.

  The first and second switches 16 and 17 are controlled by the memory 10. Specifically, the memory 10 includes a first switch control 18 that controls the state of the first switch 16 and a second switch control 19 that controls the state of the second switch 17. When the electronic circuit 1 is to be operated in the first mode, the memory 10 closes the first switch 16 by supplying a corresponding signal via the first switch control 18. Further, the memory 10 opens the second switch 17 by supplying a corresponding signal via the second switch control 19. By activating the first and second switchable resistors 13, 14, the sensitivity required in the first mode is achieved.

  When the electronic circuit 1 is switched to the second mode, the memory 10 opens the first switch 16 and closes the second switch 17. As a result, the first and second switchable resistors 13 and 14 can be deactivated.

  Further, the switchable resistors 13 and 14 can be adjusted by the memory 10. Specifically, the memory 10 includes a first adjustment control 22 and a second adjustment control 23 for adjusting the first and second switchable resistors 13 and 14, respectively. As a result, the switchable resistors 13 and 14 can be finely adjusted. As a result, variations in sensitivity in the first mode are reduced. This variation is caused not only by the resistance but also by the variation of the entire microphone. Therefore, overall variation can be reduced. Specifically, sensitivity adjustment can be achieved by adjusting the second switchable resistor 14. Furthermore, specifically, the current consumption and THD performance of the microphone can be adjusted by adjusting the first switchable resistor 13.

DESCRIPTION OF SYMBOLS 1 Electronic circuit 2 Microphone 3 Transducer 4 1st terminal 5 Voltage source 6 Resistor 7 3rd terminal 8 2nd terminal 9 Capacitor 10 Memory 11 Control input 12 Clock input 13 1st switchable resistance 14 2nd switchable Resistor 15 further resistor 16 first switch 17 second switch 18 first switch control 19 second switch control 20 transistor 21 further component 22 of electronic circuit first adjustment control 23 second adjustment control 24 signal input

Claims (15)

An electronic circuit for a microphone,
And a first pin and a second pin,
The electronic circuitry is selectively operable in a first mode or a second mode, wherein in the first mode, the first pin is configured for microphone output, in said second mode the second pin is an electronic circuit configured for microphone output. Electronic circuit according to claim 1, further comprising a memory for setting the electronic circuits in the first or second mode. At least one electronic circuit according to claim 1 or claim 2 wherein comprises a switchable resistance. In the first mode, the electronic circuit according to claim 3, wherein said switchable resistor is switched on. Wherein the first and second mode, the first electronic circuit of any one of pin is configured for power section 1-4. And a signal input for receiving the transducin service or al signal, the switchable resistor is claim 3 or are disposed electrical path between said signal input second pin 4. The electronic circuit according to 4 . Electronic circuit according to any one of claims 1 to 6, comprising a third pin configured for ground. Comprising a signal input for receiving the transducin service or al signal, a third and a terminal configured for ground, said switchable resistor is between the signal input and said third pin The electronic circuit according to claim 3 , wherein the electronic circuit is arranged in an electric circuit of At least one of the switchable resistors, electronic circuit according to claim 2, further comprising at least one switch the notes of Li to thus controllable for switching on the switchable resistor. Electronic circuit according to any one of the claims 3, 4, 6, 8 and 9 switchable resistance is adjustable. Comprising at least one switchable resistor, the switchable resistor are possible adjustment, wherein the memory is an electronic circuit according to claim 2, wherein to control the adjustment of the switchable resistors.   The electronic circuit according to claim 1, wherein the electronic circuit is an application specific integrated circuit (ASIC). Microphone comprising an electronic circuit according to any one of claims 1 to 12, and transducin support. The transducin Sa is a microphone of claim 13, wherein created by MEMS (microelectromechanical systems) technology. A method for operating a microphone according to claim 13 or 14,
Selecting the first or second mode;
Method comprising the steps of operating in a mode that has been selected the microphone.

Images